Finite element analysis in adjacent segment degeneration after lumbar fusion

✍ Scribed by Jia-Zhi Yan; Gui-Xing Qiu; Zhi-Hong Wu; Xue-Song Wang; Ze-Jun Xing

• Publisher: Wiley (Robotic Publications)
• Year: 2011
• Tongue: English
• Weight: 147 KB
• Volume: 7
• Category: Article
• ISSN: 1478-5951
• DOI: 10.1002/rcs.374

✦ Synopsis

Abstract

Background

Adjacent segment degeneration (ASD) following lumbar fusion has been well documented in recent years. However, the pathogenesis of ASD is not clear. To investigate this issue, we established a finite element model of segments L2–L5, simulated a single‐segment posterior fixation in L3–L4 and investigated the stress variation and the effects of the instrumented lumbar posterior fixation on adjacent levels.

Methods

Models A, B and C of L2–L5 multisegment finite element intact models were established. In model A, segment L3–L4 was not fixed and was without disc degeneration in the adjacent segment (L2–L3, L4–L5); in model B there was posterior pedicle fixation in segment L3–L4 without disc degeneration in the adjacent segment (L2–L3, L4–L5); in model C there was posterior pedicle fixation in segment L3–L4 with a degenerated disc in the adjacent segment (L2–L3, L4–L5). Four levels of axial pressure, 0.3, 0.5, 1.0 and 2.0 MPa, were compared between each model of the stress variation on the discs of the adjacent segment (L2–L3, L4–L5).

Results

The maximum principal stress mean value of disc L2–L3 under four pressures in model A was determined. The statistical results showed that stress was not significant difference in disc L2–L3 between models A and B, but there was a significant difference in disc L2–L3 between models A and C and a significant difference between each group in disc L4–L5 under four pressure conditions.

Conclusions

The preoperative degeneration of the adjacent segment of the disc is a significant risk factor for ASD. Copyright © 2011 John Wiley & Sons, Ltd.